Cornus canadensis

bunchberry dogwood

Cornaceae

The Basics

USDA Plant Database

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Magnoliophyta (flowering plants). Class - Magnoliopsida (dicotyledons). Subclass - Rosidae. Order - Cornales. Family - Cornaceae (dogwood family). Genus - Cornus L. (dogwood) Species -Cornus canadensis L.

Throughout North America, bunchberry dogwood occurs in coniferous, deciduous, and mixed forests in elevations between 0-1,500 m. Bunchberry dogwood is more commonly associated with conifers than hardwoods, and it is particularly widespread in the understory of spruce and fir forests. Bunchberry dogwood is rarely restricted to particular moisture conditions or soil types, so it is less commonly an indicator species but, generally, it's found in the understory of cool, temperate and boreal forest types. Bunchberry dogwood is usually recognized as an understory dominant in habitat and community classifications throughout its range (FEIS).

Cornus canadensis provides low to moderate food and cover for small mammals and birds. It has a state protection status of 'Threatened' in Iowa and Ohio and 'Endangered' in Illinois, Indiana, and Maryland (USDA).

In western North America, Cornus canadensis is the principal understory species in the following forest types: white spruce (Picea glauca), paper birch (Betula papyrifera), and white spruce- paper birch types in Alaska and western Canada; pacific silver fir (Abies amabilis)- western hemlock (Tsuga heterophylla)) in the Pacific Northwest; western redcedar (Thuja plicata)- western hemlock in Montana and Idaho and east of the Cascade Range in Oregon, Washington, and southern British Columbia; and in aspen (Populus tremuloides) types across western North America. Cornus canadensis is associated with understory species such as Oregon boxwood (Paxistima myrsinities), Alaska blueberry (Vaccinium alaskensis, and other Vaccinium spp.), twinflower (Linnaea borealis), and sword fern (Polystichum munitum) (FEIS).

Identification

Bunchberry dogwood is a low-growing, mostly herbaceous perennial that often forms patches or clumps from extensive, creeping rhizomes. Stems are slender, typically less than 25 cm tall, and somewhat woody at the base. Leaves are firm and occur in false whorls of 4 to 7 near the top of stems. Whorls of 6 leaves are typical of flowering stems; whorls of 4 are typical of sterile stems. Individual bunchberry dogwood flowers are very small and occur in a terminal cyme surrounded by 4 showy, petal-like bracts. There are typically 10 to 25 flowers per inflorescence. Fruits are clusters of small (5-8 mm), 2-seeded, berry-like drupes.

Threats

Bunchberry dogwood is rarely killed by forest disturbances, but abundance of bunchberry dogwood is often lower on disturbed than undisturbed sites, which may relate to the disturbance itself or changes in the mircoenvironment resulting from the disturbance. In mixed-conifer forests impacted by the eruption of Mount St Helens, bunchberry dogwood frequency was greater in scorched areas (33%), where trees were killed but remained standing, than in blow down areas (15%), where trees were killed and snapped or uprooted.

Bunchberry dogwood is typically only top-killed by fire; postfire sprouting is common. Rhizomes typically reach the mineral soil layer and are covered by about 4-13 cm of duff or soil. With reproductive organs at these depths, bunchberry dogwood is considered intermediate in fire damage resistance among ground cover species in British Columbia's Douglas-fir forest zone. It is generally expected to survive fires that fail to raise soil temperatures appreciably or produce long-term soil heating. Bunchberry dogwood rhizomes are sensitive to heating; therefore, on sites where rhizome depths do not penetrate beyond the duff layer or the top few centimeters of mineral soil, bunchberry dogwood may not survive fires that consume the entire duff layer.

Abundance of bunchberry dogwood can be reduced by logging. Bunchberry dogwood cover was negatively correlated (r = -0.650) with mechanical site treatments, when cleared and mechanically treated boreal and sub-boreal sites were visited 10 years after logging. In the Cascade Range in Oregon and Washington, bunchberry dogwood occurred in young, mature, and old-growth Douglas-fir forests, but development was best in old-growth stands. It was considered sensitive to disturbance based on the evaluation of experimental stands that were logged, clearcut, and/or slash burned (FEIS).

Reproduction

Flowering and Fruiting - Bunchberry dogwood produces flowers that are pollinated by bees, flies, and various other insects. Wind pollination was suspected in Isle Royale National Park, MI, after researchers protected flowers from insects and found that 3 of 9 protected inflorescences produced seed. Bunchberry dogwood flowers are equipped with an appendage that explosively releases pollen when touched. The speed of pollen release was sufficient to lodge pollen into an insect's hairs, and in the field, insects that triggered flower explosions were coated with pollen (FEIS).

Seedling Development - Studies often report poor seed production by bunchberry dogwood; however, seed production may increase with increased light availability. Weather conditions and flowering date can also affect seed production. While the age at which wild-growing bunchberry dogwood plants produce flowers and fruits was not reported in the available literature (as of 2011), in a nursery setting, bunchberry dogwood plants grown from seed took 5 years to produce flowers (FEIS).

Vegetative Reproduction - Bunchberry dogwood clones can be extensive, but the size of clones and abundance of nodes and sprouts along rhizomes vary by site and are likely greater in high-light environments. In southeast Alaska, an individual clone was found to have a rhizome length of 436 cm and was estimated to be 36 years old. The longest internode legnth found was 75 cm and occured in an area where the rhizome grew through decayed logs (FEIS)

Species Distribution

Bunchberry dogwood is a widely distributed, partially circumboreal species. In North America, it occurs throughout Canada, Alaska, and other northern US latitudes. Bunchberry dogwood is much less common and often restricted to cool, moist, and/or high-elevation sites in its southern US range (FEIS).

Citation

FEIS Fire Effects Information System (FEIS), USDA. 2012. Cornus canadensis.

Seven Oaks Native Nursery 2020. Cornus canadensis.

USDA Plants Database USDA, NRCS. 2020. The Plants Database. National Plant Data Team, Greensboro, NC 27401 USA.

UTofA Lady Bird Johnson Wildflower center University of Texes at Austin, 2016. The Plants Database. TWC staff, TX 78739 USA.